Can't register license file for Messaging Gateway 10.0.1

I'm trying to register license file, but keep getting error message as below:

Connection error 6: Couldn't resolve host 'register.brighmail.com'

I have an appliance installed with Messaging Gateway 10.0.1 and locally created LAN so it's not connected to our production network.

I've created a small network to connectio two appliances and a laptop that I'm connected to the appliance via SSH and via web browser to register.

And, this laptop is connected to internet via wifi.

Thanks in advance for your help!